Press cylinder for paper machines and pulp drying machine



June 3, 1969 o. H. MESKANEN 3,447,451

PRESS CYLINDER FOR PAPER MACHINES AND PULP DRYING IACHINE Filed June 1. 1966 Sheet of 2 OLAVI Ii HESKAMEA 11v VFW TIE June 3, 1969 o. H. MESKANEN 3,447,451 PRESS CYLINDER FOR PAPER MACHINES AND PULP DRYING MACHINE Filed June 1, 1966 Sheet 4? of 2 FIGZ 0L AV/ nanny "(YEA TOR AMG United States Patent Int. (:1. B30b 9/20, 9/00 US. Cl. 100-121 2 Claims ABSTRACT OF THE DISCLOSURE A press cylinder for paper machines and pulp drying machines has two hollow cylinders located one within the other and firmly engaging each other without play, the inner cylinder having a greater thickness than the outer cylinder, both cylinders having a large number of substantially uniformly distributed perforations, the outer cylinder having a larger number of perforation than the inner cylinder, the perforations of the outer cylinder being smaller than those of the inner cylinder, the perforations of the inner cylinder having enlarged outer portions, substantially all perforations of the outer cylinder registering with the perforations of the inner cylinder and at least two perforations of the outer cylinder partly coinciding with a perforation of the inner cylinder.

The present invention has reference to a press cylinder with through holes for paper machines and pulp machines. lt is previously known practice to use in the press sections of paper machine and pulp drying machines as one of a pair, a cylinder, the mantle of wihch has been pierced with drilled holes. These holes have enabled the water released from the web to be dried to pass into this cylinder, from where it has been drained through the end of the cylinder. It has likewise been a known procedure to apply vacuum inside the perforated cylinder at the pressure point to boost the removal of water at the pressure point. At the other component of the pair also a cylinder with holes not extending through the mantle has been used. The water released at the pressure point is then pushed into these holes and is subsequently removed from them at a point outside the pressure area. Another previously known modification is to use a press cylinder with grooves on its outside, the water released at the pressure point being able to enter these grooves and subsequently being removed from them outside the pressure zone.

The following drawbacks are to be observed in these previously known cylinder designs: In the case of a cylinder with through holes, the hole density has to be kept low, about 150200 holes per dm. of the outer cylinder surface, in order that the cylinder might retain sufficient strength. Since the holes are thus spaced rather far apart on the outer surface of the cylinder, the water has to travel a long distance on the cylinder surface before it encounters the nearest hole. Application of vacuum within the cylinder increases the speed of water transfer, but it involves high expenditures. A great difiiculty encountered With cylinders having holes which do not pass all through the mantle is that the holes become plugged and the water removing capacity of the press is impaired. The disadvantage of a grooved cylinder is excessive wear of the press felts, because the grooves are provided on the rubberized cylinder and deformations of the grooving ensue at the pressure point, which causes a stress on the felt.

The present invention provides the creation of a press cylinder with through holes which is free of the above- 3,447,451 Patented June 3, 1969 ice mentioned drawbacks and which operates well without vacuum acting inside the cylinder. The press cylinder is most appropriately composed of two coaxial, hollow cylinders placed inside each other, with their meeting mantle surfaces joined with shrink fit over the entire length of the mantle, and with the irmer cylinder attached to the shaft journals at its ends. The inner, thick-walled cylinder acts as load-supporting frame of the combination and it is perforated by holes of 4-5 mm. diameter passing through the mantle, which are fluted to become 8 mm. in diameter at their outer end, the hole density being -200 holes per din. of the outer surface of said cylinder. Since the inner cylinder furnishes requisite strength to the combination, the outer cylinder may be thin-walled and provided with a substantially denser perforation than the inner one. This latter perforation consists of holes passing through the cylinder mantle and having a diameter of 2.5-3.5 mm., that is, considerably smaller than the diameter of the holes in the inner cylinder, and the perforation density being 400-500 holes per drn. of the outer mantle surface of this latter cylinder. The holes are so placed in the outer cylinder that they always encounter a hole in the inner cylinder, in other words, that they coincide at least partially with a hole of the latter. The outer cylinder may be made up of two or several short cylinder sections of the kind described, placed end to end over the inner cylinder.

The following advantages are gained with a press cylinder according to the present invention. The hole density on the outer surface of the press cylinder can be made as high as 400-500 holes per (1111. of the outer mantle surface of the cylinder, by which the water removing capacity of the press is essentially improved because the flow path of the water on the cylinder will be only 30-50% of what it is on existing perforated cylinders, before the water encounters a hole. The resistance to flow is consequently considerably reduced. It follows that it is possible to remove more water at the pressure point unchanged line pressure. The shorter horizontal flow paths enable the web to be dried to be subjected to higher pressure in the press without danger of marking or crushing of the web. A higher dry content is thus obtained when a cylinder according to the present invention is used, even at high machine speeds and with reasonable operating costs, without impairment of the web quality.

The invention shall be described in greater detail in the following, with reference to the form of its realization presented in the accompanying figures. FIGURE 1 shows a cross section through part of a press cylinder according to the present invention. FIGURE 2 shows an end view, on partial section, of a pair of cylinders in the press section of a felt drying press when the lower cylinder at the press point has been made according to the present invention. FIGURE 3 is a schematical representation of the press section of a paper machine provided with press cylinders according to the present invention.

The press cylinder according to the present invention, shown in FIGURE 1, is composed of a thin, hollow outer cylinder 1 and a hollow inner cylinder of considerably greater wall thickness 2 placed inside the former and with its outer mantle surface adjoining without play to the inner surface of the outer cylinder, and both cylinders being rigidly coupled together. The inner cylinder 2 constitutes the load-bearing frame of the composite press cylinder. The mantle of the inner cylinder 2 is uniformly perforated by holes 3 passing through the mantle and having an enlargement 4 at their outer ends. As has been said before, the diameter of these holes is most appropriately made to be 45 mm. and the outer-end diameter of their enlargement most appropriately 8 mm., and the perforation density, as has also been said before, is most appropriately made to be 150-200 holes per dm. of the outer mantle surface. The mantle of the outer cylinder is likewise perforated by through holes 5, which have a considerably smaller diameter than those in the inner cylinder, for instance 2.53.5 mm., and a considerably higher hole density than in the inner cylinder, for instance 400500 holes per dm. of the outer mantle surface. The holes in the mantle of the outer cylinder 1 always coincide with the enlarged end of some hole or holes 3 in the mantle of the inner cylinder. A hOle 3 in the mantle of the inner cylinder is thus able to drain the water coming from several holes 5 in the mantle of the outer cylinder.

At the pressure point shown in FIGURE 2, the lower cylinder 6 is one according to the present invention. Thus, it has an outer cylinder 1 and an inner cylinder 2 and these cylinders are perforated as has been described above (holes 5 and 3 respectively), although for the sake of clarity only one hole at the pressure point has been indicated in the figure. The upper cylinder at the pressure point consists of a hollow, rubber-coated cylinder 7, its mantle being perforated with through holes 8, of which only one hole at the pressure point has been indicated. Inside the upper cylinder 7 there is a stationary pressure box 9, from which compressed air is impelled through the groove 11 in the sliding block to the pressure point. This compressed air jet blows the water detached by the pressure from the felt through the holes in the cylinder 6 built according to the present invention, into the cylinder. Inside the lower cylinder 6, oscillating nozzles 12 have been arranged, which direct a high pressure jet towards the holes of the cylinder, the jet passing through the holes in the cylinder to the splash trough 13 and cleaning the said holes in its passage. The outer surface of the lower cylinder 6 is kept clean in a manner previously known in itself, by the aid of an oscillating scraper 14. It may be mentioned that the other cylinder working at the presure point against a cylinder according to the present invention may as well be a cylinder of some other kind than that specifically described above, for instance an unperforated rubbercoated cylinder.

In FIGURE 3 a pressure arrangement has been shown in which a press cylinder according to the present invention is employed. In this arrangement, the fibre substance web 15 travels together with the felt 16 over the feltguide roller 17 to the paper drying press consisting of a rubber-coated upper cylinder 18 and a lower cylinder 19 according to the present invention. After leaving the pressure point, the fibre web passes over the paper guideroller 20 and the felt alone is carried by the felt guiderollers 21 and 2.2 to the felt drying press, consisting of a rubber-coated upper cylinder 23 with, perforated mantle and a lower cylinder 24 acording to the present invention. Moreover, compresed air is blown through the upper cylinder to the pressure point. After leaving the felt drying press, the felt passes over felt guide-roller 24 and over the tension and guide-rollers 25 and 26 back to the felt guide-roller 17.

Applications of the present invention are by no means restricted to the arrangement described as an example above. For instance, of the pair of mating press cylinders at the pressure point at least one is a cylinder according to the present invention, but the other one may equally well be a cylinder of some other kind than described in the foregoing. The mating cylinders at the pressure point must not necesarily be positioned one straight above the other.

What I claim is:

1. A press cylinder for paper machines and pulp drying machines, comprising two hollow cylinders located one within the other and firmly engaging each other, the inner cylinder having a greater thickness than the outer cylinder, both cylinders having a large number of holes, the outer cylinder having a larger number of holes than the inner cylinder while the holes of the outer cylinder are smaller in size than the holes of the inner cylinder,

the holes of the inner cylinder each having enlarged outer portions, at least two holes of the outer cylinder partly coinciding with a hole of the inner cylinder, substantially all holes of the outer cylinder registering with the holes of the inner cylinder.

2. Press cylinder according to claim 1 characterized in that the hole density of the inner cylinder is 150-200 holes per dm. of the outer surface of its mantle, the diameter of the holes is 4-5 mm. and the hole density of the outer cylinder is 400-500 holes per drn. of the outer surface of its mantle, the hole diameter being 2.5-3.5 mm.

References Cited UNITED STATES PATENTS 358,974 3/1887 Grimm -121 714,856 12/1902 Birkholz 100-121 1,793,688 2/1931 Gardella 29-130 X 2,069,448 2/ 1937 Ireland et a1. 2,798,424 7/1957 Smith et a1. 100-121 X 2,876,697 3/1959 Van Tillo 100-121 3,097,995 7/1963 Beachler 162-372 X PETER FELDMAN, Primary Examiner.

US. Cl. X.R. 

